The present disclosure relates to polarization separation devices, which may be used in image display systems. In particular, the present disclosure relates to reflective and transmissive polarizing beam splitters (PBSs), which may be used in image display systems that incorporate polarization-rotating, image-forming devices.
Image display systems incorporating PBSs are used to form images on viewing screens, such as projection displays. A typical image display system incorporates an illumination source that is arranged so that light rays from the illumination source reflect off of an image-forming device or imager that contains the desired image to be projected. The system folds the light rays such that the light rays from the illumination source and the light rays of the projected image share the same physical space between a PBS and the imager.
The imager of the image display system is typically a polarization-rotating, image-forming device, such as a liquid crystal on silicon (LCoS) device, which operates by rotating the polarization of the light rays. LCoS imagers are polarization rotating, which means that polarized light rays are either transmitted with their polarizations substantially unmodified for the darkest state or transmitted with their polarizations rotated to provide a desired gray scale. Thus, an input beam comprising polarized light rays is generally used for illuminating an LCoS imager.